Plumb Bob your Wall to Get it Straight

Jim Mallery

In the first part of this series, you learned about the Pythagoras 3-4-5 triangle and the marvelously accurate 90-degree angle it creates. In part two you found out how to take the warp out of walls with a straight-edge extension, so that you can get a fairly accurate reading for plumb from a bubble (spirit) level.

Now, in this third and final article of the series, you will learn about the truest measure for plumb--the plumb bob. If you live in an old house where floors have settled, you probably have become acutely aware of the problems of leaning walls.

Forget the sad jokes surrounding the term "plumb"--like why the Little Jack Horner rhyme couldn't really have happened (his house was out of plumb). The plumb bob has been around in some form seemingly forever. Simply put, it is a string with a weight on it. Nowadays, the bob usually has a pointed tip for truly accurate measurements. Hang the bob from something, and it will drop straight in relation to gravity, aside from altering factors such as a strong wind.

What About Bob?

You can make a plumb line with some cotton string and a weight of some sort--fishing sinkers work well. A chalk line is a type of plumb bob, great for snapping a straight line down a wall to guide a wallpaper or tile layout. A chalk line works well when there is no wind, but it is a little light to hold its own in a breeze. You can buy a good plumb bob for a few dollars in the tool department of your local Big Box store.

Using the bob to plumb a wall is simple. At one end of the wall, tap a nail into the top plate so that an inch or more remains. Loop the string of the plumb bob around the nail so that the bob is just barely off the floor. Wait for the bob to quit moving (use your fingers to stop the oscillations if you are impatient). Then adjust the wall so that the distance of the line from the wall at the top is the same as the distance at the bottom. It's an easy measurement, and it's a very accurate plumb!

Multiple Measures

Anchor the wall in its plumb position, then plumb and anchor the other end of the wall. If you have a long wall, especially if you have been stuck with some shoddy, crooked framing lumber, plumb the center of the wall also.

Here is a tip to keep the string from slipping on the nail and letting the bob clunk to the floor: Wrap the string around the nail three or four times. Then make a loop with the loose end of the string, putting your finger through the loop and spinning it three times. Put the twisted loop over the nail and pull it tight. The string won't slip.

So now you have learned how to build square and plumb straight. If your door still swings open or shut by itself, don't blame the spirit level, blame the spirits.

About the Author

Jim Mallery, a semi-retired journalist and onetime registered contractor, has extensive experience remodeling, repairing, and rebuilding homes.

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